tests/api/graph: Ensure tests pass with all requests-mock versions

requests-mock recently changed its way to match URLs, paths are now
quoted when registering mocked URLs.

As Web API graph endpoint send HTTP requests to the Graph service
with SWHIDs in URL paths (containing ':' characters), those must
also be quoted or recent requests-mock will not find the registered
mocked URLs.

Also ensure tests still pass with older requests-mock versions.

See https://github.com/jamielennox/requests-mock/commit/f072845